1. Field of the Invention
The present invention relates to a compressor controlling apparatus and method, and, more particularly, to a compressor controlling apparatus and method that is capable of starting a compressor while pressure equilibrium is achieved.
2. Description of the Related Art
A compressor is mounted in an air conditioner or a refrigerator, as a part of a refrigerating cycle, to compress an operating fluid introduced into the compressor and to discharge the compressed operating fluid.
FIG. 1a shows the construction of an air conditioner with a conventional singular compressor mounted therein. An outlet pipe 3 of a compressor 1 is connected to an outdoor heat exchanger 10 via a four-way valve 9. The outdoor heat exchanger 10 is connected to an expansion unit 11 via a coolant pipe, and the expansion unit 11 is also connected to an indoor heat exchanger 12 via another coolant pipe. An outlet of the indoor heat exchanger 12 is connected to an inlet of the compressor 1 via an accumulator 13 and a low-pressure pipe 8. In this way, a closed circuit is formed in the air conditioner.
In the past, a state in which pressure equilibrium is reached has not been considered. This has been true not only when the compressor 1 is initially operated but also when the compressor 1 is operated again after the operation of the compressor 1 is stopped. As a result, a pressure difference between the outlet and the inlet of the compressor is large when the compressor is started. As a result, overload may be caused, which leads to poor start-up of the compressor.
FIG. 1b shows the construction of an air conditioner with conventional plural compressors mounted therein. Outlet pipes 3 and 4 of compressors 1 and 2 are commonly connected to a high-pressure pipe 7, which is connected to an outdoor heat exchanger 10 via a four-way valve 9. The outdoor heat exchanger 10 is connected to an expansion unit 11 via a coolant pipe, and the expansion unit 11 is also connected to an indoor heat exchanger 12 via another coolant pipe. An outlet of the indoor heat exchanger 12 is connected to inlets of the compressors 1 and 2 via an accumulator 13 and a low-pressure pipe 8. In this way, a closed circuit is formed in the air conditioner.
When an operational load is small and where plural compressors are mounted in an air conditioner, one of the compressors is operated while the other compressors is/are not operated. As the operational load is increased during the operation of the compressor, the non-operated compressor(s) is/are operated as necessary.
To this end, the high-pressure pipe is commonly connected to the outlet pipes of these plural compressors. Consequently, when only one of the compressors is operated, high-pressure coolant gas that is discharged from the operated compressor may be introduced into the non-operated compressor. To prevent damage from this phenomenon, reverse-flow preventing check valves 5 and 6 are provided at the outlets of the plural compressors, as shown in FIG. 1b. 
However, the presence of the check valves 5 and 6 do not completely prevent the introduction of the high-pressure coolant gas into the non-operated compressor. As a result, some of the coolant gas is introduced into the non-operated compressor through the corresponding check valve. When the non-operated compressor is started while the coolant gas is held in the non-operated compressor, the pressure at the outlet of the non-operated compressor is higher than usual. Thus, the pressure inside the non-operated compressor is also high. As a result, an outlet valve, which serves to supply compressed coolant to the outlet pipe, is not opened when the non-operated compressor is started. Consequently, the compressor is poorly started, and reliability of the compressor is deteriorated.